A reply to Mr. Robin's remarks on the Essay upon distinct and indistinct vision published at the end of Dr. Smith's Complete system of optiks / by James Jurin.
- James Jurin
- Date:
- 1739
Licence: Public Domain Mark
Credit: A reply to Mr. Robin's remarks on the Essay upon distinct and indistinct vision published at the end of Dr. Smith's Complete system of optiks / by James Jurin. Source: Wellcome Collection.
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![[ >6 ] ever entered, I was obliged to make an bexperi- ment to determine it in the cafe of light falling perpendicularly upon glafs; and thereby I found, that about T-s4 of the incident light was reflected back at the firft furface of the glafs. I then proceeded farther to enquire into the quantity of light refledted back Irom the firll furface of other pellucid bodies ; as alfo into the caufe why that quantity is different in different pellucid fubftances: and herein I met with great affiftance from two Principles eftablilhed by Sir Ifaac Newton. One is, c that thofe furfaces of tranfparent fubftances, which moft ftrongly refradt the in¬ cident light, do alfo moft ftrongly refledl it. The other principle is, d that every ray of light is fometimes in a difpofition to be eafiiy tranfmitted, and at other times in a difpofition to be eafiiy refledted ; and that thefe two different difpofitions return alternately at equal diftances. This engaged me toconfider attentively, what confequences tending to my purpofe might be drawn from thefe two Principles and thofe ob- fervations of Sir Ifaac Newton on which they are founded. And as Mr. Robins, though he has condefcended to borrow fome of thefe from me, yet feems not at all to underftand fome others of them, I fhall here lay them down more explicit¬ ly, as fo many diftindt Propofitions, the truth of which will eafiiy appear to thofe who have carefully perufed Sir Ifaac Newton's obferva- tions. Prop o • b Efiay, art. 224. c Opticks, Book 2. Part 3. Prop. 1. d Ibid. Book 2,](https://iiif.wellcomecollection.org/image/b30780287_0024.jp2/full/800%2C/0/default.jpg)
